1. Field of the Invention
The present invention relates to a wrapping method using a vertical, inclined or horizontal type wrapping machine for wrapping foods such as loaves of bread, wads of noodles or the like with synthetic resin film.
2. Prior Art
Wrapping machines of various types have been known, and particularly, horizontal type wrapping machines have been widely used in various industries with a view to avoid contamination of products and maintain their commercial values.
FIG. 4 illustrates the configuration of a conventional wrapping machine.
As shown in FIG. 4, a conventional wrapping machine is typically driven by a motor a and has a conveyer S provided with a number of partitions b, b . . . that divide the surface of the conveyor into so many compartments, adjacent to which is located a film feed section CS comprising a feed roller e for feeding film a from d roll of film C, a bag shaper f of a known type for rounding the film d to give it a cylindrical shape, a center sealer g for sealing the lateral edges of the cylindrically rounded film d by heat-sealing to form a tube of film d' and a delivery path i for moving said tube of film d' in the direction of arrow h, said wrapping machine further comprising a top sealing section TS in which a rotary melt-cutter 1 having a pair of heated melt-cutting blades j, k, is provided.
With a conventional wrapping machine as described above, the motor a imparts a desired constant running speed to the conveyer S, which carries food products such as wads of noodles or bags of soup B, B . . . one by one in its compartments formed by partitions b, b, . . . and delivers them to the film feed section CS.
The film feed section CS comprises a roll of film C and a center sealer g, which further comprises a guide roller g1 and a melt-bonding roller g2 to melt-bond both lateral edges of the film to form a tube of film d' so that the delivered products go into the tube of film d' one by one with a constant interval. Then in the top-seal section TS, the tube of film d' containing said products B, B . . . is melt-cut by the rotary melt-cutter 1 which rotates in synchronism with the movement of the tube of film d' and melt-cuts the film at the lines marked on the film d but not shown in the drawing so that the products B, B . . . are separated from one another as the forward end and the rearward end of the wrapping film of each product are melt-bonded and cut to form an individual packet m.
In a conventional wrapping machine as described above, said conveyer S, film feed section CS and top seal section TS are operated synchronously by supplying said film feed section CS and top seal section Ts with mechanical power from the conveyer S, which is driven by the motor a, by way of chain driving mechanisms represented by broken lines M1 and M2 in the drawing so that products B, B . . . are wrapped at a rate of, for example, about 100 products per minute.
A conventional wrapping machine as described above is particularly prone to trouble at the top seal section TS, because if any one of the products B, B . . . is located incorrectly within the tube of film for some reason or another, the rotary melt-cutter 1 can cut into not only the tube of film d' but the product B contained in it. If such an accident happens, the operation of the machine is automatically stopped by a detector mechanism and the supply of electricity to the motor a is interrupted. This interruption of power supply inevitably stops the operation not only of the top seal section TS but also of the film feed section CS and all the other moving sections.
Consequently, the operator who is supplying pieces B, B, . . . to feeding conveyor S has to temporarily stop his operation for corrective measures. If such interruptions occur frequently, it can not only significantly deteriorate his or her performance but also increase his or her physical fatigue and a considerable amount of time and labor will be consumed to remove the faulty product and resume the wrapping operation.
There has been proposed and actually used a number of preventive measures for this kind of troubles by which the operation of the wrapping machine is automatically stopped whenever an incorrectly placed product is detected. However, while such measures can prevent cutting of products in a wrapping machine, the machine automatically comes to a complete halt when an incorrectly placed product is found, thereby reducing the efficiency of the machine and causing a considerable loss of time and labor for the resumption of operation.
It is therefore an object of the present invention to provide a wrapping method which is free from the above described problems and according to which the conveyer, the film feed section and the top sealing section of a wrapping machine are driven by their respective driving motors which are logically coordinated so that, even if one of the component units is stopped, the operation of the other units is maintained without interruption. With this method, the servomotor or motor provided with an inverter which is used for driving the top sealing section is controlled by appropriately utilizing rotary angle signals coming from the conveyer and a cut-in warning signal which is produced wheneven an incorrect placement of a product is detected in such a manner that, when the product whose faulty positioning has been detected reaches the top sealing section, the operation of only the melt-cutting blades is temporarily stopped and, after the product has been moved away from the section, the melt-cutting blades return to their normal operation with the product immediately after the faulty one, thereby ensuring normal operation of the conveyer and the film feed section including the center sealing unit during the temporary stop of the operation of the cutting blades and consequently eliminating any loss of labor and time required for the resumption of operation so that a considerable improvement of operational efficiency may be achieved.